THEORIES OF URIC-ACID SYNTHESIS.Although most physiologists have adopted the theory of the formation of uric acid by an oxidative transformation of purins arising in intermediary metabolism, there is another possible mode of origin which can not be dismissed without due consideration. I refer to the direct synthesis of uric acid. That nucleic acid can be synthesized and the construction of the purin nucleus become possible in mammals is beyond question in the case of developing and growing animals living on a practically purin-free dietary.20 That uric acid itself is formed by synthetic processes in birds is also verified beyond doubt. In mammals the end product of nitrogenous exchange is quite different, however. When the synthesis of uric acid had been accomplished in the laboratory repeated attempts were made to induce an analogous formation in animals. Horbaczewski's artificial synthesis from urea and glycocoll could not be imitated by feeding